header {
  width: 100vw;
  height: 100vh;
  background-image: url("https://api.ixiaowai.cn/api/api.php");
  background-repeat: no-repeat;
  background-size: cover;
  background-position: top center;
  /*设置背景图片为顶部居中，用于兼容小尺寸设备体验*/
}
header > nav {
  width: 100vw;
  height: 65px;
  display: flex;
  position: fixed;
  top: 0;
  left: 0;
  z-index: 9000;
  transition: 200ms;
  justify-content: center;
  align-items: center;
  background-color: rgba(0, 0, 0, 0.6);
  padding: 0px 6vw;
}
header > nav h1 {
  margin-right: auto;
  font-size: 32px;
  color: white;
  cursor: pointer;
  transition: 400ms;
}
header > nav h1:hover {
  color: gray;
}
header > nav > ul {
  display: flex;
  height: 100%;
  list-style: none;
}
header > nav > ul > li {
  display: flex;
  justify-content: center;
  align-items: center;
  height: 100%;
  padding: 0px 8px;
  transition: 400ms;
  transition-delay: 50ms;
}
header > nav > ul > li:hover {
  background-color: white;
}
header > nav > ul > li:hover a {
  color: black;
  font-weight: 900;
}
header > nav > ul > li:hover i {
  color: black;
  font-weight: 900;
}
header > nav > ul > li > i {
  color: white;
  margin-right: 5px;
  transition: 400ms;
  transition-delay: 50ms;
}
header > nav > ul > li > a {
  color: white;
  transition: 400ms;
  transition-delay: 50ms;
}
header > nav #header_nav_span {
  display: none;
}
header div {
  width: 100vw;
  height: 100vh;
  position: absolute;
  top: 0;
  left: 0;
  padding: 0px 60px;
  display: flex;
  flex-direction: column;
  justify-content: center;
  align-items: center;
  background-color: rgba(0, 0, 0, 0.4);
  transition: 200ms;
}
header div *:nth-last-of-type(n+1) {
  margin-bottom: 35px;
}
header div *:nth-last-of-type {
  margin: 0;
}
header div h2 {
  display: flex;
  color: white;
  font-size: 28px;
}
header div p {
  color: white;
  font-size: 18px;
  text-align: center;
}
header div a {
  color: white;
  padding: 8px 22px;
  text-align: center;
  background-color: #87CEEB;
  border-radius: 50px;
  font-size: 16px;
  transition: 400ms;
}
header div a:hover {
  background-color: white;
  color: #87CEEB;
}
